Special Features

Social Media

ESE Supplies Item Glossary

Acid

In conservation, having a pH of under 7. Acidic substances can
weaken the cellulose in paper materials, often causing the paper to
become brittle and/or discolored.

Acid-free

Implies that a material has a pH of 7 or higher. However, this may
only be true at the time of manufacture. Substances found in some
papers such as lignin and certain additives may still lead to the
formation of acid over time.

Acrylic

The term "Acrylic" most commonly refers to Polymethyl
Methacrylate. Polymethyl Methacrylate is abbreviated PMMA and is
typically used in the lenses of exterior lights of automobiles.
Acrylic has a density that is less than half the density of glass,
and similar to that of other plastics. Acrylic has good impact
strength, higher than that of glass or polystyrene, but
significantly lower than that of polycarbonate or engineering
polymers. In the majority of applications, Acrylic will not shatter
but instead breaks into large dull pieces. Acrylic is softer and
more easily scratched than glass. Scratch-resistant coatings (which
may also have other functions) are often added to Acrylic sheets.

Alkaline

In conservation, having a pH of over 7. Alkaline substances such
as magnesium carbonate and calcium carbonate may be added to a
material to neutralize the acids contained within or as an alkaline
reserve or buffer.

Alkaline Reserve

An alkaline substance often added to paper storage materials to
counteract the acids that may form in the future and to help absorb
acids from artifacts. Alkaline-buffered storage materials usually
have a pH of between 7.5 and 9.

Archival

A term often used to describe various materials, it is meant to
imply that the materials in question are of a quality that is
appropriate for artifact storage or treatment. This may or may not
be true. The word archival is not strictly defined or regulated, and
therefore may be used at will by manufacturers.

Buffer

See Alkaline Reserve

Burst Strength

The force of pounds per square inch required to rupture or burst
the side of a cardboard box and is determined by the Mullen Test.
This method indicates the box's ability to withstand external or
internal forces and how the box will contain its contents during
rough handling. For example, a box with a burst strength of 200 lbs.
per sq. inch indicates that the cardboard used to make the box can
withstand 200 lbs. of pressure per square inch.

Cellulose

The structural component of the primary cell wall of green
plants, many forms of algae and the mycetes. Some species of
bacteria secrete it to form biofilms. Cellulose is the most common
organic compound on Earth. About 33 percent of all plant matter is
cellulose (the cellulose content of cotton is 90 percent and that of
wood is 50 percent). For industrial use, cellulose is mainly
obtained from wood pulp and cotton. It is mainly used to produce
paperboard and paper; to a smaller extent it is converted into a
wide variety of derivative products such as cellophane and rayon.

Clay Coated News Back

Clay Coated News Back is abbreviated CCNB and is a recycled
paperboard. Recycled paperboards are made from pre-consumer and
post-consumer waste. Pre-consumer waste is mill conversion waste.
Post-consumer waste consists of paper products that have been used
and discarded. Recycled paperboard is six to nine ply, and has less
desirable qualities than Solid Bleached Sulfate (SBS). Clay Coated
News Back is typically coated with a thin layer of kaolin clay over
a top ply of white recovered fiber to improve its printing surface.

Conservation

The treatment of artifacts to help extend their survival and
usefulness while at the same time maintaining their original
integrity as much as is possible.

Copolymer

A material whose chemical structure is made of long chains of two
differently structured chemical units (Monomers) which repeat a more
or less regular pattern in the chain.

Corrugated Paper Board

Corrugated Paper Board is more commonly known as "cardboard".
Corrugated board is made largely of recycled paper and most commonly
is comprised of three components: an outer and inner liner, and a
corrugating medium, commonly referred to as the "fluting", which is
glued between the liners. It is this sandwich-type construction that
gives corrugated board its excellent rigidity and structural
strength as well as its unique cushioning characteristics. Over the
decades, corrugated board has evolved and developed to provide a
wide range of products for different applications. Standard and
non-standard categories of corrugated board are based on the type of
flute, whether coarse, fine or extra fine and the number of fluted
walls whether single, double or triple layered.

Die

A die is a specialized tool used in manufacturing industries to
cut or shape material using a press. Like molds and stencils, dies
are generally customized to the item they are used to create.
Products made with dies range from simple paper clips to complex
pieces used in advanced technology.

Edge Crush Test

The Edge Crush Test (ECT) measures the stacking strength of
corrugated cardboard boxes or fiberboard. Determining a finished
box's compression strength is defined by the amount of force that is
needed to crush cardboard by standing it on its edge. This test is
also measured in lbs. per square inch. For example, a box with an
ECT of 32 lbs. per square inch indicates that the board, standing on
edge, can withstand a force of 32 lbs. per square inch before
crushing.

Elastomer

A thermoset or thermoplastic with long polymer chains
cross-linking during curing. The elasticity is derived from the
ability of the long chains to reconfigure themselves to distribute
an applied stress. The covalent cross-linkages ensure that the
elastomer will return to its original configuration when the stress
is removed. As a result of this extreme flexibility, elastomers can
reversibly extend from 5 to 700%, depending on the specific
material. Without the cross-linkages or with short, uneasily
reconfigured chains, the applied stress would result in a permanent
deformation. Elastomers that have cooled to a glassy or crystalline
phase will have less mobile chains, and consequentially less
elasticity, than those manipulated at temperatures higher than the
glass transition temperature of the polymer.

Encapsulation

Involves placing a document between two sheets of transparent
polyester film, then sealing all four edges of the film. This
provides the document with support and helps protect it from
possible damages incurred through handling. Encapsulation differs
from lamination in that the document is not adhered to the
polyester, but instead may be removed at any time by cutting along
the edges of the polyester. Encapsulation is not suitable for all
documents, as the microclimate inside the capsule may actually
accelerate the deterioration of an acidic document. For this reason,
a sheet of alkaline buffered paper is often included behind a
document in an encapsulation to help absorb some of the acids.
Encapsulation is particularly appropriate for very brittle or
fragile documents, and for those documents that will be handled
frequently.

Extrusion

One of the most common plastics processing techniques covering a
vast range of applications in which resins are melted, heated and
pumped for processing. Extrusion machines accomplish these tasks by
means of one or more internal screws. In extrusion, the material to
be processed is sheared between the root of the screw and the wall
of the barrel that surround it. This process produces frictional
energy that heats and melts the substance as it is conveyed down the
barrel. Melted extrudate from the machine is further processed after
the extrusion phase, which typically produces pellets, sheet, cast
film, blown film, fibers, coatings, pipes, profiles or molded parts.

Flute

Flute size refers to the number of flutes per lineal foot in
corrugated paper, although the actual flute dimensions for different
corrugated manufacturers may vary slightly. Measuring the number of
flutes per lineal foot is a more reliable method of identifying
flute size than measuring board thickness, which can vary due to
manufacturing conditions. Common flute sizes are "A", "B", "C", "E"
and "F". The 'B' flute is the most widely used. It is very difficult
to crush and has good compression strength. The 'C' flute is larger
with greater compression strength but offers less crush resistance
and requires more space.

GSM

Grams per Square Meter: The standard unit of measure for the
weight of paper or fabric.

Heat Sealing

The process of joining two or more thermoplastic films or sheets
by heating areas in contact with each other to the temperature at
which fusion occurs, usually aided by pressure. When the heat is
applied by dies or rotating wheels maintained at a constant
temperature, the process is called thermal sealing. In impulse
sealing, heat is applied by resistance elements which are applied to
the work when relatively cool and then rapidly heated. Simultaneous
sealing and cutting can be performed by this method.

High Density Polyethylene

High Density Polyethylene is abbreviated HDPE and is another
chemically stable plastic often used for storage of paper artifacts.
It is the most widely used plastic, with an annual production of
approximately 80 million metric tons. Its primary use is within
packaging (notably the plastic shopping bag). Polyethylene is not
considered biodegradable, as it takes several centuries until it is
efficiently degraded, except when exposed to UV from sunlight. SPI
resin identification Recycling No. 2

Hindered Amine Light Stabilizers

Hindered Amine Light Stabilizers is abbreviated HALS and is a
group of additives having a common chemical structure as part of
their molecule. These highly effective UV stabilizers protect the
polymer by scavenging free radicals.

Injection Molding

A manufacturing process for producing parts from both
thermoplastic and thermosetting plastic materials. Material is fed
into a heated barrel, mixed, and forced into a mold cavity where it
cools and hardens to the configuration of the mold cavity. After a
product is designed, usually by an industrial designer or an
engineer, molds are made by a mold maker (or toolmaker) from metal,
usually either steel or aluminum, and precision-machined to form the
features of the desired part.

Kraft Paper

A paper produced by a modified sulfate process using only wood
pulp. It is a relatively coarse paper and is known especially for
its strength. Grocery bags are typically made of kraft paper.

Kraft Process

The kraft process (also known as kraft pulping or sulfate
process) describes a technology for conversion of wood into wood
pulp consisting of almost pure cellulose fibers. The process entails
treatment of wood chips with a mixture of sodium hydroxide and
sodium sulfide, known as white liquor, that break the bonds that
link lignin to the cellulose.

Lap Joint

A joint made by lapping one material over another to provide a
mated area that can be joined with an adhesive.

Lamination

A process, not often used anymore by conservation professionals,
by which a document is reinforced with transparent sheets of
plastic. The high heat and pressure used during lamination, together
with the instability of the materials used and the difficulty of
removing the item from the laminate has made this method a generally
unacceptable practice for items of any enduring value or importance.

Lignin

A component of the cell walls of plants. Lignin is unstable,
light sensitive, and breaks down into acid compounds as it ages. Its
presence in paper items contributes to their degradation over time.
Lignin is found in large amounts in wood, the plant fiber most often
used to make paper since the middle of the 19th century. Lignin can,
to a large extent, be removed during the papermaking process,
resulting in a higher quality paper.

Linerboard

Linerboard is the grade of paperboard used for the outer
"facings" of a corrugated box. Kraft linerboard is made from wood
fiber derived by the kraft process and typically contains no more
than 20 percent recycled material.

Linear Low Density Polyethylene

Linear Low Density Polyethylene is abbreviated LLDPE and is used
predominantly in film applications due to its toughness, flexibility
and relative transparency. LLDPE is the preferred resin for
injection molding because of its superior toughness and is used in
items such as grocery bags, garbage bags and landfill liners.

Low Density Polyethylene

Low Density Polyethylene is abbreviated LDPE and is commonly used
in flexible bags for dry cleaning, trash, produce and bread, shrink
wrap, and in some rigid containers for food storage. LDPE is
slightly waxy, flexible, and stretches. It floats on water and
smells like a candle when burned. Recycled LDPE is often used to
make grocery bags, agricultural film, and plastic lumber. SPI resin
identification Recycling No. 4.

Micron

A micrometer or micron is one millionth of a meter, which is
equivalent to one thousandth of a millimeter or one thousand
nanometers. The micrometer is a common unit of measurement for
wavelengths of infrared radiation. The name micron is used,
especially in astronomy and in the semiconductor industry, to denote
a micrometer.

Migration

The ability of a chemical or compound to move from one material
to another. One example of migration is acid migration which is when
acid moves from an acidic material to a material of lesser or no
acidity. This can be seen in the form of the brown marks on the
pages of a book from a newspaper clipping placed within.

Mil

A unit of thickness often used when describing plastics used for
the storage and treatment of artifacts. One mil (.001) equals one
thousandth of an inch.

Monomer

An atom or a small molecule that has the potential of chemically
binding to other monomers of the same species to form a polymer. The
most common biochemical monomer is glucose, which is linked by
glycosidic bonds into polymers such as cellulose and starch, and is
over 76% of the weight of all plant matter.

Neutral

In conservation, having a pH of 7; in other words, neither
alkaline nor acidic.

Newsprint

A low-cost, low-quality, non-archival paper. It is usually made
by a mechanical milling process, without the chemical process that
is usually used to remove lignin from the pulp. The pages of a comic
book are typically made from recycled newsprint.

pH

A measure of acidity or alkalinity. The pH scale runs from 0 to
14. Each number increment indicates an increase of tenfold. Neutral
pH is 7. Any number below 7 is acidic, with 1 being the most acidic.
Any number above 7 is alkaline, to a maximum alkalinity of 14.

Phthalates

Also known as phthalate esters, are esters of phthalic acid and
are mainly used as plasticizers which are substances added to
plastics to increase their flexibility, transparency, durability,
and longevity. Phthalates are primarily used to soften polyvinyl
chloride (PVC).

Plastic

One of many high-polymeric substances, including both natural and
synthetic products, but excluding the rubbers. At some stage in its
manufacture, every plastic is capable of flowing, under heat and
pressure if necessary, into the desired final shape.

Plasticizers

Additives that increase the plasticity or fluidity of the
material to which they are added. These materials include plastics,
concrete, wallboard, and clay. Although the same compounds are often
used for both plastics and concrete the desired effect is slightly
different. Plasticizers for concrete soften the mix before it
hardens, increasing its workability or reducing water, and are
usually not intended to affect the properties of the final product
after it hardens. The plasticizers for plastics soften the final
product increasing its flexibility.

Point

A unit of thickness often used when describing paper or board.
One point equals one thousandth of an inch and is equivalent to one
mil. For example, paper that is 40 mils in thickness (.040) is
referred to as a 40-point paper.

Polyester

One of the plastics that are recognized as being safe for storage
of paper artifacts because of its chemical stability. Frequently
used for sleeves, folders and encapsulations, conservation grade
polyesters are Mylar D and Melinex 516 by DuPont.

Polyethylene Terephthalate

Polyethylene Terephthalate is abbreviated PET and is a
thermoplastic polymer resin made from polyester. Polyethylene
Terephthalate is also called PETE, PETP, and PET-P. PET is referred
to as simply polyester while PET is most often used to refer to
packaging applications. SPI resin identification Recycling No. 1.

Polymer

A large molecule (macromolecule) composed of repeating structural
units typically connected by covalent chemical bonds. While polymer
in popular usage suggests plastic, the term actually refers to a
large class of natural and synthetic materials with a wide variety
of properties.

Polypropylene

The third chemically stable plastic often used in the manufacture
of enclosures for storing paper artifacts. Polypropylene sheets,
also referred to as pages, are a popular choice for trading card
collectors. These sheets come in various configurations, the most
popular of which is the nine pocket page for standard size trading
cards. Trading cards are inserted into each pocket and the pages are
then stored in a binder. SPI resin identification Recycling No. 5.

Polystyrene

An inexpensive hard thermoplastic substance, which is in solid
(glassy) state at room temperature. The outside housing of the
computer you are using now is probably made of polystyrene. Model
cars and airplanes are made from polystyrene, and it also is made in
the form of foam packaging and insulation (StyrofoamTM is one brand
of polystyrene foam). Clear plastic drinking cups are made of
polystyrene. So are a lot of the molded parts on the inside of your
car, like the radio knobs. Polystyrene is also used in toys, and the
housings of things like hairdryers, computers, and kitchen
appliances. SPI resin identification Recycling No. 6.

Polyvinyl Chloride

Polyvinyl Chloride is the plastic known at the hardware store as
PVC. This is the PVC from which pipes are made, and PVC pipe is
everywhere. The plumbing in your house is probably PVC pipe. The
"vinyl" siding used on houses is made of Polyvinyl Chloride. Inside
the house, PVC is used to make linoleum for the floor. PVC is useful
because it resists two things that naturally oppose each other: fire
and water. Because of its water resistance Polyvinyl Chloride is
used to make raincoats and shower curtains. It also has flame
resistance because it contains chlorine. PVC can degrade as it ages,
emitting hydrochloric acid, which can be very damaging to
paper-based collectables. Flexible vinyl products contain additional
chemicals to change the physical properties of the material called
plasticizers which can migrate. SPI resin identification Recycling
No. 3.

Radio Frequency Welding

Radio Frequency Welding is also known as RF Welding. Two pieces
of material are placed on a table press that applies pressure to
both surface areas. Dies are used to direct the welding process.
When the press comes together, high frequency waves (usually 27.12
MHz) are passed through the small area between the die and the table
where the weld takes place. This high frequency field causes the
molecules in certain materials to move and get hot, and the
combination of heat and pressure causes the weld to take the shape
of the die. This type of welding is used to connect polymer films
used in a variety of industries where a strong consistent leak-proof
seal is required. The most common materials used in RF welding are
PVC and polyurethane. It is also possible to weld other polymers
such as nylon, PET, EVA and some ABS plastics.

Solid Bleached Sulfate

Solid Bleached Sulfate is abbreviated SBS and is a premium
paperboard grade that is produced from a furnish containing at least
80% virgin-bleached wood pulp. Most bleached paperboard is coated
with a thin layer of kaolin clay to improve its printing surface and
may be also coated with polyethylene resin for wet strength food
packaging.

Stabilizers

Stabilizers increase both virgin resin's and post-consumer
plastic's strength and resistance to degradation. Heat stabilizers
provide resistance to thermal degradation during periods of exposure
to elevated temperatures. Thermal degradation is reduced not only
during processing but also during the useful life of the finished
products. Light stabilizers are used in a variety of resins to limit
the effects of sunlight or other sources of ultra violet radiation.
Antioxidants can be used as sacrificial additives to protect
plastics from oxidizing environments.

Thermoplastic

A polymer that turns to a liquid when heated and freezes to a
very glassy state when cooled sufficiently. Most thermoplastics are
high molecular weight polymers whose chains associate through weak
Van der Waals forces (as in polyethylene); stronger dipole-dipole
interactions and hydrogen bonding (as in nylon); or even stacking of
aromatic rings (as in polystyrene). Thermoplastic polymers differ
from thermosetting polymers in that they can be melted and remolded.

Thermoset

A polymer material that irreversibly cures. The cure may be done
through heat, through a chemical reaction (two-part epoxy, for
example), or irradiation such as electron beam processing. Thermoset
materials are usually liquid or malleable prior to curing and
designed to be molded into their final form, or used as adhesives.
Others are solids like that of the molding compound used in
semiconductors and integrated circuits.

UV Absorbers

Abbreviated UVA, UV Absorbers are a group of additives which
protect organic materials by absorbing the UV radiation

UV Barriers

A class of UV Absorbers which totally block UV light.

UV Stabilizer

Any chemical compound which, when admixed with a thermoplastic
resin, selectively absorbs UV rays and minimizes chemical and/or
physical changes that may be engendered by UV.

UV Radiation

The range of electromagnetic radiation from 150 to 400
nanometers. In solar radiation, there is a significant amount only
over 250 nanometers.